n to believe, from some interesting
observations made by Mr. W. Thompson, of Belfast, that some sessile
cirripedes moult about every fortnight.

_Internal Structure of the Cup._--When the cup is dissolved in acid,
each shelly layer is represented by a rather tough, pale-brown membrane,
itself composed of numerous fine laminae, which, under a one-eighth of an
inch object glass, exhibit generally only the appearance of a mezzotinto
drawing; but there often were layers of branching vessels, (like
moss-agate,) less than the 1/10,000th of an inch in diameter, and of a
darkish colour; these vessels are not articulated, but otherwise
resemble the same peculiar structure in the valves of the capitulum. The
exterior yellow membrane is marked, or rather composed of successive
narrow rims, which, in fact, are the lines of termination of the laminae
of membrane, which in a calcified state form the cup itself. In most
parts, both on the borders and under the centre of the cup, but not
everywhere, there are imbedded in the yellow membrane, elongated,
irregular, top-shaped masses of bright yellow chitine, each furnished
with a tubulus, which penetrating the calcareous laminae leads to the
corium; the little apertures thus formed, are clearly visible in the
layers of membrane, left after exposure to acid. In _L. Nicobarica_, the
innermost shelly layer of the cup was punctured, like the surface of the
shell in Chthamalus and many other sessile Cirripedes, by the internal
orifices of these tubuli. The top-shaped masses often have star-shaped
summits; and they differ in no essential respects from those on the
lower part of the peduncle, excepting that they are quite imbedded in
the membrane covering the under surface of the cup, whereas those on the
peduncle project freely. I found these top-shaped bodies in the outer
membrane of the cups in _L. dorsalis_, _L. cauta_, and _L. Rhodiopus_,
which alone I was enabled to dissolve in acid; and I mention this fact,
as indicating the probable presence of the more important star-headed
projections on the lower parts of the peduncle in these same species.
The basal calcareous cup resembles, in essential structure, the valves
of the capitulum; the chief difference being that in the former there is
a larger proportion of animal matter or membranous layers.

After the dissolution of the cups, in _L. dorsalis_ and _L. Rhodiopus_,
I most distinctly traced the two cement-ducts; they included the usual
d